Top illumination projectors or "episcopes" have been known for decades. The picture to be projected is illuminated by a powerful light source and its image is formed on a screen or board or wall by means of a deflecting mirror system and a projection optic system. In conventional episcopes, the picture is disposed on or beneath the episcope's picture scene and remains accessible to the user. After projection, the picture is manually exchanged, and this handling is difficult and complicated.
Therefore, a previous attempt has tried to mechanize the exchange of the pictures. West German Patent DE-PS No.162 085 describes and illustrates a design wherein the pictures are piled in a compartment and are conveyed by an endless transporter chain individually from the picture scene into a collecting container. This episcope is intended to be used as a movie projector. In the design disclosed in West German Patent Publication DE-OS No. 21 28 117 pictures wound on a drum are projected, or card-shaped pictures are transported by means of a revolving conveyer belt across the picture scene.
In the first-mentioned design it is assumed but not expressively said that the individual pictures which all have the same dimensions are sufficiently thick and stiff to be engaged by the transporter chain and pushed away from the picture scene, and that with a speed sufficient for movie projection. The pictures must be rearranged after the projection so that they will lay in the initial sequence in the pile again. The last-mentioned drawback is inherent to the second design mentioned above, too, in case of loose cards being processed, and the cited publication does not disclose how to solve the problem of removing individual pictures from the pile and to convey them in an accurate position through the episcope.